Cyclin D1/D2-CDK4 Drives Cell Migration by Orchestrating Cytoskeletal Dynamics Through a TGFβ-FAK-Rac1 Axis

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Cyclin D-CDK4/6 complexes classically regulate cell cycle progression.
• Emerging evidence suggests these complexes also influence cell migration.
• The precise mechanisms linking CDK4/6 to cytoskeletal dynamics in cell motility were unclear.

Purpose of the Study:

• To investigate the role of CDK4/6 in cytoskeletal remodeling and cell migration.
• To elucidate the molecular pathways affected by CDK4/6 inhibition in HeLa cells.
• To determine if CDK4/6 inhibitors could impact tumor invasion.

Main Methods:

• CDK4/6 inhibition in HeLa cells.
• Analysis of lamellipodia formation, focal adhesion assembly, cell migration, and invasion.
• Proteomic and phosphoproteomic analyses.
• Western blotting for protein phosphorylation and GTPase activity.
• Rescue experiments with Rac1 or FAK activation.

Main Results:

• CDK4/6 inhibition disrupted lamellipodia formation and focal adhesion assembly, reducing cell migration and invasion.
• CDK4, complexed with cyclin D1/D2, localized to membrane ruffles, facilitating cytoskeletal reorganization.
• CDK4 inhibition attenuated the TGFβ pathway by reducing Smad3 phosphorylation, downregulating integrin subunits.
• CDK4 inhibition decreased FAK and Rac1 activation; Rac1 or FAK activation restored migration defects.

Conclusions:

• Cyclin D1/D2-CDK4 promotes Smad3 phosphorylation, upregulating integrins and activating FAK/Rac1 for lamellipodia formation and cell migration.
• CDK4 directly regulates actin cytoskeletal reorganization during cell migration.
• CDK4/6 inhibitors may reduce cytoskeleton-dependent tumor invasion alongside antiproliferative effects.